Molecular pathology and diagnosis of infectious diseases

The authors have reviewed and described molecular methods for the detection of etiologic agents or genetic sequences involved in the pathogenesis of various diseases. Molecular probes are now available for the rapid diagnosis of diseases caused by a large number of viruses, bacteria, fungi, spirochetes, rickettsia, and other infectious agents. Since nucleic acid probes can distinguish minute differences indicative of genetic mutations or alternations, specific probes also can be developed even for those diseases with unknown causative agents or etiologies. Further, using these techniques, specific drug-resistant and pathogenic strains associated with epidemics in widely separated areas of a country or a town have been identified. Thus, the sensitivity and specificity of molecular detection methods using both radioactive and nonradioactive probes are at a point that clinical specimens can be tested for rapid diagnosis and identification of etiologic agent(s) that may be responsible for the pathogenesis of a wide variety of diseases.

A simple procedure for maximum yield of high-quality plasmid DNA

We have established a simple procedure for the rapid isolation of high-quality plasmid DNA suitable for various molecular techniques and provided a step-by-step protocol. The DNA samples isolated by this procedure have been used successfully for double-stranded DNA sequencing, restriction enzyme mapping, subcloning, in vitro mutagenesis, generation of deletion clones and so on. The procedure is highly reproducible, and superior quality DNA can be obtained without the use of phenol, chloroform or other organic solvents.

Interferon-alpha maintenance therapy after cytotoxic chemotherapy for treatment of acquired immunodeficiency syndrome-related Kaposi's sarcoma

A prospective phase I clinical trial with recombinant interferon-alpha-2b as maintenance therapy after cytotoxic chemotherapy was conducted. Twenty-one homosexual and bisexual males with extensive mucocutaneous or visceral epidemic acquired immunodeficiency syndrome (AIDS)-Kaposi's sarcoma (KS) were studied. After a complete response (6 patients) or partial response (15 patients) from chemotherapy consisting of Adriamycin (20 mg/m2), bleomycin (10 U/m2), and vincristine (1.4 mg/m2; 2 mg maximum), patients were given interferon-alpha (IFN-alpha) in an attempt to prolong disease-free survival. Three dose levels of daily IFN-alpha were tested: 5, 10, and 15 million U. The maximum tolerated dose was 10 million units. Dose-limiting toxicities included recurrent grade 3 fatigue, diarrhea, and fever, which resulted in the termination of therapy in eight patients (38%). Hematologic toxicities were infrequent (four patients; 19%). Responses were observed in two patients on IFN-alpha, both at the 10-million-U dose level. The median duration of response on IFN-alpha therapy following chemotherapy was 8 weeks (range, 3-11). We conclude that the duration of IFN-alpha maintenance response following cytotoxic chemotherapy is short with response to residual disease observed in a minority of cases at this dose and schedule. Additional trials of maintenance therapy in patients with advanced AIDS-KS combining antiretroviral agents are in progress.

AIDS and HIV associated disorders in Karachi

In a seroepidemiological study for the prevalence of HIV infection in Pakistan, individuals from different groups were tested for HIV antibodies using ELISA. Positive results were confirmed by western blot. Out of 413 individuals screened four were found positive by ELISA, of these three were confirmed by western blot. Two cases were foreign nationals visiting Pakistan, one of them died of full blown AIDS, the other did not show any AIDS related condition. The third case was a Pakistani national who presented with full blown AIDS with toxoplasmosis. To our knowledge this is the first case of full blown AIDS reported in a Pakistani national. The fourth case was an asymptomatic promiscuous lady who could not be traced further. Blood transfusions abroad and sexual contacts were responsible for HIV infection in these cases.

A multicenter clinical trial of oral ribavirin in HIV-infected people with lymphadenopathy: virologic observations. Ribavirin-LAS Collaborative Group

A double-blind, randomized, placebo-controlled trial comparing two daily doses of oral ribavirin (600 and 800 mg) and a placebo was performed at four medical centers geographically distributed throughout the USA. One hundred and sixty-four HIV-infected adult men with lymphadenopathy were enrolled over a 2-month period and received active treatment for 24 weeks followed by a 4-week interval during which they did not receive the study drug. A marked interlaboratory variation in HIV isolation from peripheral blood mononuclear cells was observed, underscoring the critical role of quality assurance in similar multicenter trials. Nevertheless, the combined data indicate that ribavirin did not significantly suppress HIV activity (on measurement of reverse transcriptase activity) after week 6 or reduce serum p24 antigenemia.

Studies on the mode of action of non-steroid anti-inflammatory drugs

During the past decade the mode of action of anti-inflammatory drugs has mainly been related to the inhibition of prostaglandin (PGS) synthesis (Vane 1971). In a presentation by Burne (1982) it has been shown that PGS are not the only most important mediators of inflammation, and the inhibition of prostaglandin synthesis alone does not explain all common effects and mode of action of NSAIDs. Hence alternative concepts are presented in this paper, which may be adopted as the mode of action of NSAIDs.

Prevalence and significance of acquired immunodeficiency syndrome-related retinal microvasculopathy

We performed ophthalmologic examinations on 127 subjects with or at risk for human immunodeficiency virus (HIV) infection over a one-year period to determine the prevalence and significance of retinal cotton-wool spots and hemorrhages (AIDS-related retinal microvasculopathy). Of 26 asymptomatic homosexual men, of whom 13 were HIV seronegative and 13 were HIV seropositive, none manifested this retinopathy. Three of 34 patients (9%) with AIDS-related complex and 29 of 67 patients (43%) with AIDS manifested retinopathy on the initial examination. This difference in the prevalence of retinopathy between groups was statistically significant (P less than .05). Patients with AIDS demonstrated 7.2 times greater odds of manifesting retinopathy than patients with AIDS-related complex (P less than .05). Within the group of patients with AIDS, the T helper (CD4) to suppressor (CD8) cell ratio was significantly associated with retinopathy at the initial ocular examination. The CD4:CD8 ratio of the total group of AIDS and AIDS-related complex patients with retinopathy was significantly lower than that of patients without retinopathy (P less than .05). There was no significant association between retinopathy and any specific past or concurrent opportunistic infection or neoplasm. The presence of retinopathy was not associated with symptoms in any patient. The lesions of AIDS-related retinal microvasculopathy may be an important finding in the evaluation of patients suspected to have HIV-related disease.

Immunoblot reactivity of a non-HIV protein with human sera. Transfusion Safety Study Group

Examination of serum for the presence of antibodies to the human immunodeficiency virus (HIV) by immunoblot analysis requires precise identification of reactivities with various HIV specific proteins. During a recent survey of approximately 2,000 sera, we identified 22 sera from non-HIV-reactive blood donors and 2 from individuals receiving blood products for congenital blood disorders, which consistently and exclusively reacted with a protein of a molecular weight slightly greater than 65,000 daltons (termed AT65). Since the HIV pol p65 protein reacts with specific antibodies at about the same position (i.e., 65,000 daltons), it was essential to determine the viral or nonviral origin of the AT65 reactivity. Our data indicate that the AT65 reaction is due to a protein present on normal or activated lymphocytes, which can co-purify with HIV preparations used for immunoblot analysis. Recognition of HIV-specific p65 and nonspecific AT65 reactions is important to those responsible for interpretation of HIV immunoblots and may aid in the evaluation of some "indeterminant" results.

Vitamin D metabolite-mediated hypercalcemia and hypercalciuria patients with AIDS- and non-AIDS-associated lymphoma

Fifteen patients with lymphoma and hypercalcemia (greater than or equal to 11.0 mg/dL) were identified by screening the serum chemistry profile obtained from patients upon admission to the Los Angeles County/USC Medical Center. Seven of the 15 (47%) possessed a frankly elevated serum concentration of 1,25-dihydroxyvitamin D [1,25-(OH)2-D]. An additional patient with severe hypercalcemia (16.2 mg/dL) had a serum 1,25-(OH)2-D concentration in the midnormal range, not a suppressed value. To examine the potential existence of hypercalciuria in absence of overt hypercalcemia, prospective screening of 23 normocalcemic patients with lymphoma was undertaken. Four of the 23 patients (17%) had increased fractional urinary calcium excretion rates (0.35 +/- 0.3 mg calcium/100 mL glomerular filtrate [GF], mean +/- SE; normal, less than 0.16 mg/100 mL GF); two of the hypercalciuric patients had a frankly elevated serum 1,25-(OH)2-D concentration. Of the 19 hypercalcemic/hypercalciuric lymphoma patients identified, none had an elevated serum immunoreactive parathyroid hormone concentration. Fourteen of the 19 hypercalcemic/hypercalciuric patients (74%) suffered from B-cell neoplasms, three had Hodgkin's lymphoma, and two had adult T-cell leukemia/lymphoma. All hypercalcemic/hypercalciuric patients had widespread disease (stage III or IV). Six patients, four with hypercalcemia and two with hypercalciuria, had acquired immunodeficiency syndrome (AIDS). These data suggest that the deregulated synthesis of a 1,25-(OH)2-D-like metabolite is a common cause of hypercalcemia and hypercalciuria in patients with lymphoma including patients with AIDS-associated tumors.

Human immunodeficiency virus-induced cytotoxicity for CD8 cells from some normal donors and virus-specific induction of a suppressor factor

Several aspects of human immunodeficiency virus (HIV)-induced pathology in vitro warrant close examination to ascertain their role in the development of disease in vivo. The ability of HIV to produce cytopathology of CD4 cells has been well documented, although the extent and mechanism(s) may be varied. Further, immune suppression by HIV envelope (env) is well documented in vitro, but its importance in vivo remains unknown and the role of other HIV components in immune suppression has not been examined. We have exposed peripheral blood mononuclear cells (PBMC) from normal donors to ultraviolet-irradiated HIV (uv-HIV) at concentrations similar to those found in AIDS patient serum and determined that in some normal donors (3/7) depletion of CD8 cells as well as CD4 cells is demonstrable. Abrogation of phytohemagglutinin (PHA)-induced proliferation by uv-HIV was also examined in the same normal donors. Immune suppression, unlike CD4 cell killing, does not require intact virus and occurs at physiologically relevant concentrations of HIV. Furthermore, PBMC exposed to uv-HIV in the presence of PHA produce a heat- and protease-labile suppressor factor(s) following removal of virus, whether or not they are reexposed to PHA. Our results suggest that cell killing may be a more broad event than previously described, including the killing of at least CD8 cells either directly or indirectly. In addition, suppressor factors produced following exposure of patient lymphocytes to agents that induce proliferation may exacerbate the development of opportunistic infection.

Human immunodeficiency virus-associated disorders in Pakistan

We have documented evidence of the human immunodeficiency virus (HIV) infection in four individuals including a blood donor and three members of a family (husband, wife, and a child) in Karachi, Pakistan. Our data indicate that HIV has been transmitted to the wife of the seropositive male, a drug abuser, in the recent past and that she has passed the virus to her newborn child perinatally/transplacentally. The two seropositive males (blood donor and drug abuser) were diagnosed clinically as having persistent generalized lymphadenopathy, an AIDS-related condition (ARC), and the child presented with developmental disorders and neurologic manifestations. This is the first report of AIDS/ARC cases from Pakistan that can be directly related to HIV infection and its heterosexual transmission.

Human immunodeficiency virus-associated T-cell lymphoblastic lymphoma in AIDS

A patient with multiple infections whose serum had antibodies to a human immunodeficiency virus (HIV) developed a T-cell lymphoblastic lymphoma (T11+, Leu-1+, Leu-3a+, TdT+, B1-, common ALL-). Antibodies to human T-lymphotropic virus-I (HTLV-I) were absent. T-cell leukemia-lymphoma may be associated with HIV infection.

AIDS-related malignant lymphoma: results of prospective treatment trials

Twenty-two consecutive patients with high-grade, B-cell lymphomas related to the acquired immunodeficiency syndrome (AIDS) were accrued onto two sequential phase II studies, consisting of a standard regimen (M-BACOD, group no. 1, N = 13), or a novel, intensive regimen (group no. 2, N = 9), which included high-dose cytosine arabinoside (HD-Ara-C), and high-dose methotrexate (HD-MTX), in an attempt to prevent CNS relapse and improve response rates. Stage IV disease was present in 82%. Complete remission (CR) was achieved in seven of 13 patients (54%) in group no. 1, and in three of nine (33%) group no. 2 (P = NS). By multivariate analysis, the most significant factor in predicting response was a Karnofsky performance score (KPS) greater than 60 (P = .04). Three of the ten patients who achieved CR on either regimen have relapsed; in all, five of 13 patients (31%) in group no. 1 have achieved disease-free survival for more than 1 year, compared with one of nine (11%) in group no. 2. CNS progression occurred in six patients in group no. 2, and in two patients in group no. 1. Hematologic toxicity was significantly greater in group no. 2, and these patients had an increased risk of opportunistic infection (one in group no. 1 v seven in group no. 2; P less than .01). Survival was similar, with a median of 11 months in group no. 1 and 6 months in group no. 2. We conclude that the intensive regimen of combination chemotherapy described here is associated with significant risk of early death due to opportunistic infection in patients with AIDS-related lymphoma, and that progression in the CNS remains a major problem. Trials of combination chemotherapy of a less intensive nature, perhaps in combination with immunomodulators or antiretroviral agents should be explored.

Immunohistology of persistent generalized lymphadenopathy. Evidence for progressive lymph node abnormalities in some patients

Immunohistologic analysis of cellular changes in serial lymph node biopsies of eight patients with persistent generalized lymphadenopathy (PGL) syndrome was performed and correlated with clinical and laboratory findings to better determine the natural history of human immunodeficiency virus (HIV) infection. The authors observed decreased follicle size and area in the second biopsies of six of the eight patients, associated in some with increased numbers of B-cells in medullary regions (four of eight) and more involuted follicles (four of eight). Five cases showed progressively increased paracortical areas in the second biopsies, with increased numbers of T-cytotoxic/suppressor cells and decreased T-helper cells. Seven of the patients also had a progressive loss of T-helper cells in the peripheral blood. These findings provide tissue and peripheral blood evidence for progressive immunologic deterioration in some patients with PGL.

Human normal and tumor cell lines: comparison of fibronectins and collagens

Human tumor cell lines, a rhabdomyosarcoma (RD), and a fibrosarcoma (HT-1080) were distinguished from normal human fibroblasts by tumorigenicity in athymic nude mice and immunosuppressed rats and hamsters, secretion of different types of collagen and procollagen molecules, and reduced amounts of fibronectin. The fibronectins secreted by both normal and tumor cells did not show any significant structural difference and were phosphorylated only on serine residue(s). However, fibronectin secreted by the tumor cells exhibited decreased electrophoretic mobility and was associated with as yet unidentified phosphorylated macromolecules.

Cell killing by ultraviolet-inactivated human immunodeficiency virus

Extensive cell killing and cytopathology were observed within 24 hr after exposure of a clonal cell line of human T-4 lymphocytes (RH9) to culture supernatants containing human immunodeficiency virus (HIV). Ultraviolet-irradiated HIV-containing culture fluids were also capable of killing RH9 cells and of inducing specific cytopathic effects which were indistinguishable from those induced by unirradiated virus-containing preparations. The uv-irradiated HIV was incapable of forming proviral DNA using the endogenous virion genomic RNA as a template. The RH9 cells persistently infected with HIV did not release soluble cytotoxic factors to account for the cell killing observed when culture supernatants were added to uninfected RH9 cells. The fraction involved in cell killing had the hydrodynamic properties of a retrovirus. These results suggest that a virion component is responsible for cell killing by HIV.

Human T-cell lymphotropic virus type III associated disorders. The spectrum in the heterosexual population

Eleven heterosexual patients (nine women, two men) without classic risk factors for development of acquired immunodeficiency syndrome (AIDS) were seen between March 1983, and April 1985, and diagnosed as having AIDS (four), persistent, generalized lymphadenopathy (PGL) (four), or asymptomatic human T-cell lymphotropic virus type III (HTLV-III) carrier state (three). The clinical presentations and course of those with AIDS or PGL were similar to those reported in homosexual men with AIDS or PGL, with reversed T4/T8 ratio, and the presence of antibody to HTLV-III. Asymptomatic carriers had normal T4/T8 ratios, had an absence of HTLV-III antibodies, but had HTLV-III virus cultured from blood. We conclude that the heterosexual population, with or without history of sexual exposure to individuals at risk for AIDS, may develop a wide range of clinical manifestations secondary to HTLV-III, varying from AIDS to the asymptomatic carrier state.

Suramin antiviral therapy in the acquired immunodeficiency syndrome. Clinical, immunological, and virologic results

The human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV) requires reverse transcriptase for viral replication. We treated 12 patients who had acquired immunodeficiency syndrome and active HTLV-III/LAV viremia with suramin, a potent competitive inhibitor of reverse transcriptase, in six weekly induction doses of 1 g, followed by weekly maintenance doses of 500 mg. Three of eleven evaluable patients had complete inhibition of viral reverse transcriptase levels, lasting at least 18 weeks in each. Two additional patients had marked reduction in reverse transcriptase activity. Nadir serum suramin levels at the end of the induction phase correlated with the level of reverse transcriptase reduction. Toxicity included hepatic transaminase elevation, fever, malaise, rash, proteinuria, paresthesias, reversible neutropenia, and adrenal insufficiency. Objective clinical improvement was documented in 1 patient, but no patient had improvement in immune function and 7 patients had recurrent opportunistic infections. Although suramin may suppress HTLV-III/LAV viremia, its significant toxicity and lack of effect on immune variables indicate that alternative therapy will be required.

Localization of the feline sarcoma virus fgr gene product (P70gag-actin-fgr): association with the plasma membrane and detergent-insoluble matrix

The v-fgr oncogene codes for a unique transforming protein (P70gag-actin-fgr) that contains virus-specific determinants and cell-derived sequences for both a tyrosine-specific kinase domain and an actin domain. We examined the subcellular distribution of the v-fgr protein by immunofluorescence microscopy and various cell fractionation techniques. By immunofluorescence, the v-fgr protein was localized in a diffuse cytoplasmic pattern within transformed cells. The v-fgr protein was not detectable at substratum adhesion sites. Crude membrane preparations (P100) obtained from fgr-transformed cells contained elevated levels of P70gag-actin-fgr. Further analysis of membranes on discontinous sucrose gradients revealed that P70gag-actin-fgr cofractionated with plasma membranes. Using an alternate method of fractionation, we found that the majority of the v-fgr protein remained with the insoluble matrix obtained by treating cells with a buffer containing Triton X-100. When membranes were similarly treated with detergent, nearly all of v-fgr protein remained with the residual insoluble matrix. These results suggest that the transforming activity of P70gag-actin-fgr may be directed to subcellular cytoskeletal targets at or near the cytoplasmic face of the plasma membrane.

Virus-neutralizing activity, serologic heterogeneity, and retrovirus isolation from homosexual men in the Los Angeles area

Human retroviruses have been causally associated with the development of the acquired immune deficiency syndrome (AIDS) in groups of individuals at high risk including intravenous drug users, hemophiliacs, and homosexual men. Aside from classic AIDS, homosexual men also develop persistent generalized lymphadenopathy (PGL) which is considered a part of the AIDS-related complex (ARC). We have isolated 70 strains of retroviruses related to human T-lymphotropic viruses type III (HTLV-III) from patients with PGL, AIDS, or ARC. analyses of sera from these patients indicated a high degree of serologic heterogeneity in the antibody titers and their reactivities toward various HTLV-III viral proteins. In addition, we have detected virus-neutralizing antibodies in approximately 50% of the serum samples tested from patients with PGL or AIDS. This is the first comprehensive virologic and serologic report on more than 100 patients studied at one institution in Los Angeles.

Retrovirus and malignant lymphoma in homosexual men

We report malignant lymphoma in 27 homosexual men, of whom 22 had high-grade lymphomas (B-cell immunoblastic sarcoma or small non-cleaved lymphoma) and five had low-grade disease. Antibody to human T-cell lymphotropic virus type III (HTLV-III) was present in 13 (87%) of 15 with high-grade lymphoma and in two (40%) of five with low-grade disease. In contrast, only one (9%) of 11 "control" heterosexual patients with high-grade lymphoma had antibody to HTLV-III, while such antibody was found in none of 40 asymptomatic heterosexual controls and in 17 (55%) of 31 asymptomatic homosexual men. Of the homosexual lymphoma patients, 85% presented with disease in extranodal sites, including the central nervous system and rectum, and 81% had reversed T-helper/suppressor ratios. Median survival, despite treatment, is eight months. The acquired immunodeficiency syndrome-related lymphomas in homosexual men are extranodal, high-grade, B-lymphoid tumors, associated with exposure to HTLV-III and unusual clinical characteristics.

Characterization of tumor cell lines from a spontaneous rat sarcoma expressing an endogenous retrovirus

We have characterized various biologic, immunologic and growth properties of several cell lines established from a spontaneous rat sarcoma that was discovered more than 60 yr ago. The tumors consisted of mixed cell types with no detectable host cellular immune response. Cultures derived from single-cell clones of the parental cell line were non-invasive but highly tumorigenic even in adult rats. The cultured cells spontaneously released replication-competent endogenous rat type C virus which did not carry a transforming gene in its genome. Since normal cells from the same rat strain did not produce a retrovirus, it is possible that production of the endogenous retrovirus may have triggered specific cellular changes necessary for the oncogene expression and development of this tumor.

Isolation and characterization of new ecotropic murine leukemia viruses after passage of an amphotropic virus in NIH Swiss mice

Amphotropic murine leukemia viruses (MuLV-A) cause mainly lymphoma in newborn inoculated NIH Swiss mice after a long latent period of 6-12 months. Rarely, however, about 1% of the inoculated mice develop hind limb paralysis and progressive central nervous system disease. The biological properties and RNase T1-resistant oligonucleotide fingerprints of the recovered viruses from tissues of both lymphomatous and paralyzed mice inoculated with MuLV-A were analyzed. These results indicate that serial in vivo passages of MuLV-A in NIH Swiss mice lead to generation of new MuLVs of both amphotropic and ecotropic host ranges. The recovered amphotropic viruses are highly lymphomagenic and are recombinants of MuLV-A-specific oligonucleotides and endogenous mouse sequences. The ecotropic viruses fall into two groups: (1) recombinants of MuLV-A genes and NIH Swiss mouse viral or cellular sequences and (2) new ecotropic viruses with oligonucleotide fingerprints not related to any of the known MuLVs. The naturally occurring ecotropic MuLVs of the wild mice produce both lymphoma and paralysis in NIH Swiss mice. The viruses recovered from in vivo passages are mainly of ecotropic host range although dual-tropic virus activity is occasionally seen in the spleens but not in the brains or spinal cords of the lymphomatous or paralyzed mice. Oligonucleotide fingerprinting of the recovered MuLV-Es from paralyzed mice are identical to the input MuLV-Es, indicating that the parental MuLV-E alone, without recombination, is responsible for the paralytic disease.

Molecular cloning of integrated Gardner-Rasheed feline sarcoma virus: genetic structure of its cell-derived sequence differs from that of other tyrosine kinase-coding onc genes

Gardner-Rasheed feline sarcoma virus (GR-FeSV) is an acute transforming retrovirus which encodes a gag-onc polyprotein possessing an associated tyrosine kinase activity. The integrated form of this virus, isolated in the Charon 21A strain of bacteriophage lambda, demonstrated an ability to transform NIH/3T3 cells at high efficiency upon transfection. Foci induced by GR-FeSV DNA contained rescuable sarcoma virus and expressed GR-P70, the major GR-FeSV translational product. The localization of long-terminal repeats within the DNA clone made it possible to establish the length of the GR-FeSV provirus as 4.6 kilobase pairs. The analysis of heteroduplexes formed between lambda feline leukemia virus (FeLV) and lambda GR-FeSV DNAs revealed the presence of a 1,700-base-pair FeLV unrelated segment, designated v-fgr, within the GR-FeSV genome. The size of this region was sufficient to encode a protein of approximately 68,000 daltons and was localized immediately downstream of the FeLV gag gene coding sequences present in GR-FeSV. Thus, it is likely that this 1.7-kilobase-pair stretch encodes the onc moiety of GR-P70. Utilizing probes representing v-fgr, we detected homologous sequences in the DNAs of diverse vertebrate species, implying that v-fgr originated from a well-conserved cellular gene. The number of cellular DNA fragments hybridized by v-fgr-derived probes indicated either that proto-fgr is distributed over a very large region of cellular DNA or represents a family of related genes. By molecular hybridization, v-fgr was not directly related to the onc genes of other known retroviruses having associated tyrosine kinase activity.

Inherited susceptibility to retrovirus-induced transformation of Gardner syndrome cells

Skin fibroblasts from patients with Gardner syndrome (GS), those with familial polyposis coli (FPC), and spouse or unrelated controls were karyotyped and tested for various growth properties including susceptibility to transformation by viral or chemical agents. Our results indicated that based on the higher susceptibility to retrovirus-induced transformation and chromosomal aneuploidy, the GS and FPC cells could be distinguished from those of the general population with more than 70% accuracy. However, much work is in order before any biological assay can be used for clinical diagnosis of GS or FPC patients.

Nucleotide sequence of the Rasheed rat sarcoma virus oncogene: new mutations

The nucleotide sequence of the oncogene of the Rasheed strain of rat sarcoma virus was determined. The oncogene (Ra-v-ras) encodes a 29,000-dalton (p29) transforming protein. This protein is distinct from the immunologically related 21,000-dalton protein (p21) of the Harvey murine sarcoma virus in its amino terminus and in having additional mutations in its carboxyl terminus. Although the functional significance of these changes is unknown, they appear to occur only in rat sarcoma virus.

Characterization of a differentiated cat melanoma cell line

We have established several long-term cultures of a naturally occurring metastatic melanoma of a domestic cat. The cells are fully differentiated as indicated by the Fontana-Masson staining of the melanin in the perinuclear region and by electron microscopy of the cytoplasmic melanosomes in various stages of development. The melanoma cells do not produce virus particles or the major core proteins (i.e., protein with a molecular weight of 30,000) of the feline leukemia virus or the endogenous cat virus RD-114. Retrovirus is also not induced when melanoma cultures are treated with 5-iodo-2'-deoxyuridine or bromodeoxyuridine and cocultivated with susceptible cells. Treatment of cells with N6,O2'-dibutyryl cyclic adenosine 3' :5'-monophosphate or theophyllin, however, accentuates melanin production and increases the number of pigmented cells. The cultured cells develop melanotic tumors in s.c. inoculated newborn cats and athymic nude mice. As far as we can ascertain, this is the first report of a spontaneous malignant melanoma of a cat which provides an important resource for studying cell differentiation in vitro.

Resistance to fibroblasts and hematopoietic cells to ecotropic murine leukemia virus infection; an Akvr-1R gene effect

A gene named Akvr-1 segregates as a dominant allele in California wild mice (LC). Unlike Fv-1 and Fv-2 restriction alleles, the Akvr-1 confers resistance to replication of all ecotropic (N-, B-, and NB-tropic) murine leukemia viruses (MuLV-E) and prevents endogenous AKR virus-induced lymphoma/leukemia in F1 hybrids of AKR x LC. We have tested fibroblasts and hematopoietic cells from mice of defined Akvr-1 genotypes for in vitro susceptibility to various MuLV infections. Our results indicated a dominant in vitro resistance of exogenously MuLV-E infected cells carrying Akvr-1R allele although resistance was stronger in the homozygous cells than in the heterozygous cells. Moreover, resistance of cells to virus replication was not abrogated by high multiplicities of infection or by growth stimulation of hematopoietic cultures by various T- or B-cell-responsive mitogenic agents.

Feline oncornavirus-associated cell membrane antigen: a viral and not a cellularly coded transformation-specific antigen of cat lymphomas

The feline oncornavirus-associated cell membrane antigen (FOCMA) was defined as a tumor antigen common to cat lymphomas and fibrosarcomas induced by feline leukemia virus (FeLV) and feline sarcoma virus (FeSV), respectively. The antigen was recognized by sera from cats thought to be resistant to leukemogenesis. We report here that a common denominator in the activity of naturally occurring viremic cat antisera to FOCMA is, in fact, their reactivity to FeLV C antigenic determinants. The cat antisera, monoclonal antibodies to FOCMA, and monoclonal antibodies to FeLV C, all reacted in immunofluorescence assays with FeLV C-infected cells and immunoprecipitated a molecule electrophoretically indistinguishable from envelope glycoprotein of FeLV. Viremic cat antisera to FOCMA bound to budding virus particles of FeLV C-infected cells, even though some of them could not be absorbed by mature virion proteins. Thus, the unusual feature of cat antibodies to FOCMA is their binding to nascent but not to mature virus particles. FOCMA-positive cat lymphomas expressed antigenic determinants of FeLV-C gp70, with or without productive infection. FeLV-negative tumors not expressing FeLV C gp70 were also FOCMA negative. Furthermore, most of the viremic cat sera and the monoclonal antibodies to FOCMA did not react with FeSV-transformed nonproducer cells. The absence of FOCMA from these cells and from FeLV-negative lymphoid tumors and its presence in FeLV-C infected fibroblasts indicated that this antigen is virus encoded and not a cellular tumor-specific antigen.

Role of endogenous cat retrovirus in cell differentiation

Several long-term cultures were established from a spontaneous melanoma of a cat. Cells were rounded or spindle shaped and exhibited black/brown pigmentation in the cytoplasm. No virus was released from these cells spontaneously or after treatment with chemicals. However, exogenous infection of the cat melanoma cells with the endogenous cat virus RD114 resulted in remarkable morphological and functional changes. Most of the RD114 virus-infected cells exhibited multiple neuritic extensions and about 1-2% of the population showed characteristics of neuronal cells. Because human, mouse, and hamster melanoma cultures infected with various mammalian retroviruses, including the RD114 virus, did not display any morphological alteration, it is concluded that the neuronal cell differentiation in the cat melanoma cells is a consequence of its specific interaction with the endogenous cat retrovirus.

Molecular cloning, genomic analysis, and biological properties of rat leukemia virus and the onc sequences of Rasheed rat sarcoma virus

Rasheed rat sarcoma virus (RaSV) has been shown to code for a protein of 29,000 Mr not present in replication-competent rat type C helper virus (RaLV)-infected cells. This protein is a fused gene product consisting of a portion of the RaLV p15 gag protein and the transformation-specific 21,000 Mr (p21) ras protein, which is also found in Harvey murine sarcoma virus. We now report the molecular cloning of both the SD-1 (Sprague-Dawley) strain of RaLV and the transforming ras sequences of RaSV. Heteroduplex analysis of these cloned DNAs demonstrated that the RaSV ras gene (v-Ra-ras) was inserted into the rat type C viral genome with a small deletion of RaLV genetic information in the 5' region of the gag gene and that the v-Ra-ras gene (0.72 kilobase pair) is homologous to and colinear with the p21 ras gene of Harvey murine sarcoma virus (v-Ha-ras). Restriction enzyme mapping confirmed the homology demonstrated by heteroduplex mapping, showing strong site conservation of restriction endonucleases known to cleave v-Ha-ras. Cloned v-Ra-ras DNA transformed NIH 3T3 cells, inducing the synthesis of the p29 RaSVgag-ras protein.

Characterization of a highly oncogenic murine leukemia virus from wild mice

We have isolated a highly lymphomagenic wild mouse virus by passage of a weakly oncogenic amphotropic murine leukaemia virus (MuLV-A) in NIH Swiss mice. This virus is similar in host range, interference and neutralization properties to that of the inoculated amphotropic virus but is distinct from it biochemically and causes lymphomas in 90-100% of mice within 1-2 months. Our results indicate that this highly oncogenic virus is a recombinant of wild mouse MuLV-A and sequences related to env gene region of the endogenous xenotropic virus of NIH Swiss mice.

Characterization of genome structure of amphotropic and ecotropic wild mouse retroviruses

We studied the RNA genomes of several wild mouse type C retroviruses by using RNase T1-oligonucleotide fingerprinting. The amphotropic and ecotropic viruses of field strain 1504 produced very similar oligonucleotide fingerprints, but each also had several unique oligonucleotides. All of these unique oligonucleotides were located in the env gene region and were probably responsible for the host range differences between these viruses, as well as the lymphomagenic and paralytogenic properties of the viruses. We obtained similar results with the amphotropic and ecotropic viruses of another field strain (4070), which was isolated from a mouse from a different trapping area. The amphotropic viruses of several field strains (strains 1504, 4070, and 1313) were more closely related than the ecotropic viruses of different strains (strains 1504, 4070, and 4996). These findings suggested that the genetic sequences of the amphotropic viruses are more conserved than those of ecotropic viruses isolated from the same wild mice.

Isolation of feline leukemia virus from a leopard cat cell line and search for retrovirus in wild felidae

A strain of feline leukemia virus (FeLV), subgroup A, was isolated in early subpassage of a testicular fibroblast culture obtained from a captive Asian leopard cat. Neither FeLV nor RD-114 virus was recovered from cultured tissues of 15 other animals, representing eight species of wild Felidae.

Natural killer cell activity in a population of leukemia-prone wild mice (Mus musculus)

Natural cell-mediated cytotoxicity against YAC-I targets was measured in splenocytes from leukemia-prone wild mice trapped near Lake Casitas (LC) in southern California. Cytotoxicity was mediated by cells that were non-adherent to nylon wool, non-phagocytic and resistant to thy-1.2 antiserum plus complement. Natural MuLV viremia in LC mice did not impair splenic cytotoxicity against TAC-I target cells, Cells infected with amphotropic and ecotropic MuLV of wild mouse origin were not appreciably lysed by LC splenic effectors. Although variable levels of cytotoxicity were detected against TAC-1 by normal spleen cells, consistently low levels of cytotoxicity against allogenic LC lymphoma, sarcoma and carcinoma targets were found using the same splenocytes. These results indicate that LC mice possess splenocytes with the characteristics of natural killer (NK) cells as defined in inbred mice. The resistance of LC-derived targets to lysis by LC NK cells suggests that NK cells may not be involved in natural tumor immunosurveillance or that the development of spontaneous tumors may involve escape from NK-mediated effector mechanisms.

Identification and cloning of endogenous retroviral sequences present in human DNA

Using nonstringent annealing conditions and a 2.75-kilobase segment of cloned African green monkey DNA that specifically hybridizes to the proviruses of AKR ecotropic murine leukemia virus (MuLV) and baboon endogenous virus (BaEV) as a probe, we detected related sequences in three different preparations of human brain DNA fragments. The blot-hybridization pattern obtained with cleaved human DNA was similar to that previously reported for the interaction of MuLV cDNA and cleaved mouse DNA and suggested the presence of numerous copies of retrovirus-related sequences in the human genome. The labeled 2.75-kilobase fragment derived from cloned monkey DNA was used to screen a human DNA library in Charon 4A. One clone obtained hybridized to three contiguous MuLV-and BaEV-reactive fragments of the cloned monkey DNA and to multiple fragments of human DNA including a prominent 1.0-kilobase EcoRI fragment also present in the clone.

Rat sarcoma virus: further analysis of individual viral isolates and the gene product

Rasheed rat sarcoma virus, derived by in vitro cocultivation of two rat cell lines (Rasheed et al., Proc. Natl. Acad. Sci. U.S.A. 75:2972-2976, 1978), has been reported to code for a protein of 29,000 Mr, immunologically related to the 21,000 Mr src gene product of Harvey and Kirsten sarcoma viruses. Rat sarcoma virus p29 was thought to contain at least part of a rat type C virus structural protein, since antiserum prepared against whole rat virus was able to immunoprecipitate rat sarcoma virus p29 but not Harvey or Kirsten sarcoma virus p21 (Young et al., Proc. Natl. Acad. Sci. U.S.A. 76:3523-3527, 1979). We now report that antiserum directed against rat type C virus p15, but not viral p12, p10, or p27, immunoprecipitated rat sarcoma virus p29. The p15 antiserum was also able to immunoprecipitate both denatured p29 and a peptide derived by V-8 protease cleavage of p29, indicating that this antiserum contains antibodies directed against primary amino acid determinants. Finally, five separate isolates of rat sarcoma virus were found to code for p29, which indicates that a highly specific site of recombination is involved in the generation of sarcoma viruses in rat cells.

Viral susceptibility of skin fibroblasts from patients with Huntington disease

Cultured skin fibroblasts from patients with Huntington disease (HD) and age-matched controls were tested for susceptibility to vesicular stomatitis virus (VSV) and transformation by Kirsten mouse sarcoma virus (KiMSV). The HD and control cells could not be distinguished on the basis of viral replication, plaque morphology, virus yield, or susceptibility to transformation by KiMSV. These findings suggest that the HD gene product, if expressed within peripheral tissue, does not selectively alter or interfere with viral replication.

Growth properties and susceptibility to viral transformation of skin fibroblasts from individuals at high genetic risk for colorectal cancer

Growth characteristics and susceptibility to viral transformation were compared in cultured skin fibroblasts from patients with Gardner's syndrome (GS), those with familial polyposis coli (FP), asymptomatic family members, and unrelated controls. Compared to cells from unrelated controls, cells from 4 of 5 GS patients were transformed by Kirsten murine sarcoma virus at 100- to 1,000-fold increased efficiency. The transformation efficiencies of fibroblasts from 2 of 3 FP patients were 10- to 100-fold greater than those of unrelated controls. However, because the fibroblasts from some of the young asymptomatic GS and FP family members also transformed at higher efficiency than did cells from unrelated controls, long-term observation of these families is required. This would determine whether or not these members develop clinical manifestations of GS or FP and thus establish the specificitiy of this assay for detection of individuals bearing the mutant gene. Compared to fibroblasts from unrelated controls, GS and FP fibroblasts showed a twofold to threefold increased saturation density and plating efficiency, but this difference was not noted with fibroblasts from most of the asymptomatic family members.

Prevention of paralysis and suppression of lymphoma in wild mice by passive immunization to congenitally transmitted murine leukemia virus

Lake Casitas wild mice were passively immunized as newborns with antiserum to congenitally transmitted murine leukemia virus. Immunization with immunoglobulin having a high neutralizing titer to ecotropic virus and a low titer to amphotropic virus correlated with the complete prevention of paralysis and a slight (25%), but statistically insignificant, reduction in the incidence of lymphoma. Occurrence of other tumor types and total mortality rate were not affected by immunization.

Akvr-1, a dominant murine leukemia virus restriction gene, is polymorphic in leukemia-prone wild mice

We describe a restriction gene (Akvr-1, for AKR virus restriction) that is polymorphic for two alleles, Akvr-1R (restrictive) and Akvr-1r (susceptible), in a feral population of mice (Mus) musculus domesticus) at a squab farm near Lake Casitas (LC) in southern California. Akvr-1k is a dominant allele that exhibits 100% penetrance in prevention of viremia of AKR endogenous retrovirus and of virus-mediated lymphoma in LC (Akvr-1RR) X AKR F1 hybrids. The restriction phenotype segregates as a single Mendelian locus in backcrosses to AKR mice. Akvr-1R likewise is effective in restriction of NB-tropic Moloney murine leukemia virus-induced viremia and NB-tropic Friend virus-induced splenomegaly but fails to restrict expression or pathogenesis of LC-derived amphotropic retrovirus. Pleiotropic restriction of AKR, Friend, and Moloney ecotropic viruses, but not of amphotropic virus, suggests that the viral targets of Akvr-1 in the three ecotropic viruses are similar to each other and distinct from the target in the LC-amphotropic virus. The relationship of Akvr-1 to previously reported murine restriction loci Fv-1, Fv-2, and Fv-4 is discussed.

Inhibition of spontaneous transformation of rat embryo cells releasing endogenous type C virus by virus-specific antiserum

Noninbred Sprague-Dawley rat embryo cell clones predictably undergo transformation after 20-30 in vitro passages following spontaneous release of endogenous rat leukemia virus (RaLV). In the presence of RaLV-specific antiserum, virus production and infectivity were reduced and transformation was delayed from 6 to 25 weeks. Transformation was not associated with an increased expression of Kirsten murine sarcoma virus-related src gene RNA.

Different rat-derived transforming retroviruses code for an immunologically related intracellular phosphoprotein

Kirsten sarcoma virus (Ki-MSV) and Harvey sarcoma virus (Ha-MSV) are mouse-rat recombinant viruses that were originally isolated by experimental inoculation of rats with helper-independent mouse type C viruses. We have recently identified in cells transformed by Ki-MSV or Ha-MSV, a phosphoprotein, p21, coded for by Ki-MSV and Ha-MSV [Shih, T.Y., Weeks, M.O., Young, H.A. & Scolnick, E.M. (1979) Virology 95, in press]. The p21, which is not a virion structural protein, was identified with antisera prepared by transplantation in rats of syngeneic Ha-MSV- or Ki-MSV-transformed nonproducer cells. In this study, we have applied the same methodology to examine a purely rat sarcoma virus (RaSV), which was isolated in cell culture by using helper-independent rat type C viruses [Rasheed, S., Gardner, M.B. & Huebner, R.J. (1978) Proc. Natl. Acad. Sci. USA 75, 2972-2976]. We report here that this new, purely rat sarcoma virus apparently codes for a p29, which shares immunological determinants and common V-8 protease-generated peptides with the p21 of Ha-MSV. The data suggest that the RaSV has acquired genetic information with similar coding capacity to some rat genetic information with similar coding combinant viruses, Ki-MSV and Ha-MSV. Based on data obtained on the p21 of a mutant of Ki-MSV temperature-sensitive for the maintenance of transformation, we suggest that the gene in RaSV that codes for the p29 is also required for the maintenance of RaSV-induced fibroblast transformation.

Reversion of Kirsten sarcoma virus transformed human cells: elimination of the sarcoma virus nucleotide sequences

The virus-specific nucleotide sequences in the RNA and DNA of a Kirsten mouse sarcoma virus (Ki-MSV)-transformed non-producer human osteosarcoma cell clone and two subclones of these cells that reverted to a normal phenotype have been analysed by hybridization of sarcoma virus-specific complementary DNA (cDNA) to cellular RNA or DNA. Whereas the transformed clone had acquired de novo Ki-MSV sequences in the RNA and DNA of the cells, both the revertant cell lines seemed to have lost most or all of this information from the cellular nucleic acids. The DNA from the revertant cells lacked the sequences represented either in the Ki-MSV-specific cDNA or in the total cDNA of the leukaemia-sarcoma virus complex. Thus, the reversion of the virus-transformed human cells to normal morphology is associated with the loss of most or all of the proviral sequences from the cellular DNA.